The XIXth North American Testes Workshop will be held from April 18th - 21st in Tampa, Florida. The venue will be the Hyatt Regency and the meeting will occur for the third time under sponsorship of the American Society of Andrology (ASA). The first Testes Workshop was held in 1972 and since then it has become established as an investigator-initiated meeting that brings together leading investigators in testes biology. Over the past thirty-four years, attendance of the Workshop has grown and now typically attracts 250 to 300 attendees. Increasingly, the Workshop is viewed as an essential conference for trainees as evidenced by the fact that postgraduate students and postdocs - both M.D.s and Ph.D.s - make up a significant portion of the attendees. The Testes Workshop fosters vibrant communication and scientific exchange, which creates excellent opportunities for collaboration with peers and ultimately career and scientific growth ensuring that the field of testes biology will continue to advance in the future. The Workshop also attracts scientists from outside the United States as program organizers, attendees and speakers. This meeting has a long-standing tradition of recruiting several speakers from other areas of science, outside the immediate confines of male reproduction, to facilitate creative approaches to scientific problem solving. The cross-disciplinary dialogues have become one of the Workshop's main attractions. While the 2007 Workshop has the broad theme of "Chromosome structure and gene expression," it has been organized into five sessions: Sex chromosomes and genomics; Germ-line stem cells; Regulation of gene expression; Testicular somatic cells; and Testicular pathologies. Each of the two full days of the meeting will have three, 15-minute oral presentations that will be selected from abstracts submitted for presentation at the Workshop. This component was added for the first time to the 2003 Workshop, and is designed to bring reports on breaking developments to the program. Two poster sessions are also scheduled, which will be reviewed by members of the Organizing Committee. [unreadable] [unreadable] [unreadable]